Brown County is part of the Cincinnati–Middletown, OH-KY-IN Metropolitan Statistical Area.
2007 43,956 2000 42,285 1990 34,966 1980 31,920 1970 26,635 1960 25,178 1950 22,221 1940 21,638 1930 20,148 1920 22,621 1910 24,832 1900 28,237 1890 29,899 1880 32,911 1870 30,802 1860 29,958 1850 27,332 1840 22,715 1830 17,867 1820 13,356
As of the census of 2000, there were 42,285 people, 15,555 households, and 11,790 families residing in the county. The population density was 86 people per square mile (33/km²). There were 17,193 housing units at an average density of 35 per square mile (14/km²). The racial makeup of the county was 98.08% White, 0.92% Black or African American, 0.18% Native American, 0.13% Asian, 0.08% from other races, and 0.60% from two or more races. 0.44% of the population were Hispanic or Latino of any race. 29.5% were of American, 28.2% German, 10.7% English and 10.2% Irish ancestry according to Census 2000.
There were 15,555 households out of which 37.10% had children under the age of 18 living with them, 61.30% were married couples living together, 10.00% had a female householder with no husband present, and 24.20% were non-families. 20.20% of all households were made up of individuals and 8.50% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.09.
In the county the population was spread out with 27.60% under the age of 18, 8.10% from 18 to 24, 30.30% from 25 to 44, 22.40% from 45 to 64, and 11.60% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 96.80 males. For every 100 females age 18 and over, there were 94.80 males.
The median income for a household in the county was $38,303, and the median income for a family was $43,040. Males had a median income of $32,647 versus $22,483 for females. The per capita income for the county was $17,100. About 8.80% of families and 11.60% of the population were below the poverty line, including 15.20% of those under age 18 and 9.40% of those age 65 or over.